In recent years, the High-Definition Multimedia Interface (HDMI) is available that connects a video signal output apparatus, such as a camcorder, a video recorder or a tuner, and a video image display apparatus, such as a television, through one cable, and that can effect collaboration control between the apparatuses.
The HDMI is a standard extended from the preceding Digital Visual Interface (DVI) standard by arranging a function to transmit audio data as well as video data, a copyright protecting function and a color difference transmitting function for home-use AV appliances.
The video signal output apparatus is capable of obtaining information on the display performance of the connected video image display apparatus through Digital Data Channel (DDC) communication specified in the HDMI and is also capable of obtaining the address of the HDMI terminal of the connected video image display apparatus.
Also, the video image display apparatus can make, by high/low control in Hot Plug Detect (HPD) specified in the HDMI, the video signal output apparatus execute processing for DDC communication. According to Japanese Patent Application Laid-Open No. 2007-078980, the video signal output apparatus is reset by HPD control to re-obtain Extended Display Identification Data (EDID) when the video signal output apparatus transmits data other than EDID descriptions to the video image display apparatus.
Further, HDMI Ver. 1.2 and the subsequent versions have an additional function, called Consumer Electronics Control (CEC), which is capable of collaboration control between the video image display apparatus and the video signal output apparatus.
Not only the video signal output apparatus that outputs a video signal but also a video recording apparatus or the like can be CEC-controlled. According to the HDMI standard, such an audiovisual device obtains one of logical addresses 0 to 15. The video image display apparatus can control, by using the logical address, the audiovisual device to be controlled (High-Definition Multimedia Interface Specification Ver. 1.3, Nov. 10, 2006, Supplement 1).
In the HDMI standard, however, there is a limit to the number of addresses obtainable by audiovisual devices (hereinafter referred to simply as “device”) connected to the video image display apparatus, and the upper limit of the number of addresses is determined according to a kind of device (device type). For example, only three devices corresponding to Playback Device (reproducing apparatus) can obtain logical addresses. If a fourth Playback Device is connected, it obtains a logical address non-compatible with CEC control (indefinite address). The video image display apparatus cannot CEC-control the device that has obtained the indefinite address.
The technique described in Japanese Patent Application Laid-Open No. 2007-078980 relates to processing by which the video signal output apparatus is reset to re-obtain EDID, but it is a technique devised without considering CEC control on a device having an indefinite address obtained. Therefore the technique is incapable of solving the above-described problem.
While the problem has been described with respect to the HDMI standard by way of example, the problem is not limited to the one with the HDMI standard. The above-described problem also exists with whole video image display system that is capable of the collaboration control among devices and has the determined number of assignable logical numbers.